I have seen guys at sheet metal shops I've worked in use an old metal punch to fit/bang the male and female ends together on sheet metal Pittsburgh seams. It works really well and i would like to get a new one. I believe its called an "Groove Seam Punch", but i'm not sure.
I knew that it was first made to seal together a flat seam that was used to join round pipe flanges together before snap lock became common use. it has a 3"-4" handle shaft with a grove formed at one end, doesn't exactly fit on the seam but does the job. It looks to be made from forged steel.

However these guys have to be getting them from somewhere, and i cant find them. So if anyone has first hand information on the company that makes them and the distributor i can buy one through I would love to hear from you.
Thanks!

Hi, I have always gone to Machinery trade center. the were in los Angeles when I first bought mine 19 yrs old in 1984 . I know they can order this for you .Contact Steve Cashion @ 661-775-7651 he is in Santa Clarita California or check mc master carr online catalog .hopefully this helpful.